"""Device configuration for the Ekklesia Classroom shell.

Everything that has to agree about /etc/ekklesia-classroom/device.conf
reads it through here, so the dock, the notification daemon and the DVD
commands cannot drift apart over what a setting means.
"""

import math
from pathlib import Path

CONFIG_FILE = Path("/etc/ekklesia-classroom/device.conf")

TRUTHY = {"1", "true", "yes", "on", "enabled"}

# The dock is tuned for a 1080p classroom TV at 1.0. Smaller rooms with a
# 32" panel sit near the bottom of this range, a 65" set near the top.
UI_SCALE_DEFAULT = 1.0
UI_SCALE_MIN = 0.8
UI_SCALE_MAX = 1.5


def read_device_config(path=None):
    config = {}
    path = Path(path) if path is not None else CONFIG_FILE

    if not path.exists():
        return config

    for raw_line in path.read_text().splitlines():
        line = raw_line.strip()

        if not line or line.startswith("#") or "=" not in line:
            continue

        key, value = line.split("=", 1)
        config[key.strip()] = value.strip()

    return config


def enabled(config, key, default=False):
    if key not in config:
        return default

    return config[key].lower() in TRUTHY


def ui_scale(config):
    """UI_SCALE, clamped to something a classroom can actually use."""
    raw = config.get("UI_SCALE", "")

    try:
        value = float(raw)
    except (TypeError, ValueError):
        return UI_SCALE_DEFAULT

    if not math.isfinite(value):
        return UI_SCALE_DEFAULT

    return min(max(value, UI_SCALE_MIN), UI_SCALE_MAX)


# The scale the classroom's own GTK surfaces render at.
#
# UI_SCALE is applied by sway to the whole output (see classroom-scale),
# which scales Chrome, VLC and every other application along with the
# dock. Our surfaces are measured in the same logical pixels sway is
# already scaling, so scaling them here as well would apply UI_SCALE
# twice and the dock would come out half again too big.
#
# This is the seam: if compositor scaling ever has to be abandoned,
# changing this back to ui_scale(config) restores per-surface scaling
# without touching the templates.
SHELL_SCALE = 1.0


def scaled(value, scale):
    """A pixel measurement at the given scale, never smaller than 1."""
    return max(1, int(round(value * scale)))